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https://www.thingiverse.com/thing:2931422

The extra tubing is a take-up tube. Only needed for the cartridge in it's normal function. The half-moon thing is part of what holds the cartridge fast as the magnetic field of the stepper holds...

You can always feed the cartridges from outside the machine. A pole through a box can serve as a holder.

As to respooling, it is mostly a technique of getting the cartridge apart. Manipulating...